How to use the Alt + Right click in edit mode in Linux
Keyboard shortcuts on the OS override those in Blender.

Two possible solutions:


Change the keyboard shortcuts on blender and avoid conflicting key combinations.


The main disadvantage custom shortcuts is that it's hard to follow tutorials or other help. If you work with blender on other computers your shortcuts will not match. Resetting to factory defaults will also result in the loss of your custom settings (unless you save them to a file).


Reassign the keyboard shortcuts on the OS using key-combinations that are not used in blender.


(The way I deal with it is by re-assigning the Linux keyboard shortcuts so that Alt of Ctrl keys are not used by the OS, but use the super (windows) key instead).
On Linux Mint open the system settings and navigate to &quot;Windows&quot;.

and select the super key to move or resize windows:

You might have to restart Blender for all Alt-related keyboard shortcuts to work reliably.